Conventionally, an exposure device, an LED head and an image forming device include a substrate on which an LED array chip is mounted, a lens holder that supports the substrate, a rod lens array that is supported in the lens holder to face the LED array chip and that converges light irradiated from the LED array chip, a base arranged on an opposite side of a substrate mount surface, and the like. The electrostatic latent image is formed as the light irradiated from the LED array chip mounted on the substrate converges through the rod lens array and exposes the photosensitive drum arranged at an image forming position of the rod lens array. In this exposure device, a technology is known in which a mount surface is formed on the lens holder for supporting the substrate, in which both edges of the substrate contact the substrate mount surface, and in which the substrate is biased against the mount surface of the holder with a biasing member, in order to support the substrate in the lens holder.
Japanese Laid-Open Patent Application No. 2009-073041 discloses a technology to miniaturize an exposure device by engaging a first engagement part formed on a base and a second engagement part formed on an inner wall of a support member in order to assemble the base in the support member, thereby simplifying work to assemble the substrate in the support member.
However, in the conventional exposure device, LED head and image forming device, the substrate and the support member are deformed when the biasing member that biases the substrate is assembled, causing a center of the rod lens array and an optical axis of the LED array chip, which are supported in the support member, to become offset from each other. As a result, an uneven amount of light that exits from the rod lens array is generated, negatively affecting formation of latent image by the exposure device.